Sealing of variable guide vanes

ABSTRACT

The guiding device of a turbine has guide vanes which are rotatably mounted in the turbine housing. A sealing sleeve is arranged between the turbine housing and the guide vane stem. The additional axial compression spring ensures that the sealing sleeve is continuously pressed onto the guide vane mating contour, and that the axial gap and also the leakage flow are prevented as a result.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to EP Application06405370.5 filed in European Patent Office on 28 Aug. 2006, and as acontinuation application under 35 U.S.C. §120 to PCT/EP2007/058888 filedas an International Application on 27 Aug. 2007 designating the U.S.,the entire contents of which are hereby incorporated by reference intheir entireties.

TECHNICAL FIELD

The disclosure relates to the field of turbomachines. It refers to theguiding device of a turbomachine, for example of the turbine of anexhaust gas turbocharger, with rotatably mounted, variable guide vanes,and also to an exhaust gas turbocharger with a turbine with such aguiding device.

BACKGROUND INFORMATION

Exhaust gas turbines, for example of turbochargers, are used inconjunction with an internal combustion engine. The exhaust gas from theinternal combustion engine in this case is used as a propulsive meansfor driving the turbine wheel. The turbine wheel is connected by meansof a shaft to the compressor wheel, by which the inlet air, which is forfeeding to the internal combustion engine, is compressed. In order tomeet the variable operating conditions of modern engines, variableturbine geometries (VTG) can be used in exhaust gas turbines instead offixed flow cascades (nozzle ring). In this case, the angle of incidenceof turbine guide vanes can be adapted to the respective operating pointby means of an adjusting mechanism.

A VTG device as a rule comprises a plurality of guide vanes which aremounted in a bearing housing, and an adjusting mechanism for rotatingthe guide vanes. VTG devices are described for example in EP 0 226 444or DE 43 09 636.

The guide vanes of an exhaust gas turbine, which during operation arevery intensely heated, must be installed in the bearing bushes withadequate radial clearance so that in the hot operating state they do notseize in the bearing bushes. Due to the radial clearance between thebearing bushes s and the guide vane stem, a small amount of hot gasesalways escapes from the region around the guide vane into theenvironment. With increasing bearing clearance, this leakage flowthrough the bearing bush increases. This effect leads to a loss ofturbine efficiency, and also to an increased noise development, as arule in the form of a whistling which becomes more and more intense.

SUMMARY

An adjusting device for a guiding device of a turbomachine is disclosedto the effect that despite the operation-related clearance between themoving parts of the guiding device, no leakage flow, or only a slightleakage flow, escapes through the bearings of the guide vanes.

According to the disclosure, this can be realized by a sealing sleeve(also referred to as a sealing diaphragm or sealing element) beingarranged between the housing, in which the guide vanes are rotatablymounted, and the respective guide vanes.

The sealing sleeve in this case is optionally axially guided through thecylindrical outside or inside diameter of the guide bush which is usedfor support of the guide vane stem. A radial residual gap, whichpossibly remains between the sealing sleeve and the guide bush, istolerated to a minimum clearance so that only a small residual mass flowescapes through the fit.

According to the disclosure, an additional axial compression spring canensure that the sealing sleeve is continuously pressed onto the guidevane mating contour, and that the axial gap and also the leakage floware prevented as a result.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is subsequently explained in more detail with referenceto the figures. In this connection, in the drawing:

FIG. 1 shows a section through a part of an exhaust gas turbocharger, onthe turbine side, with a guiding device with variable guide vanes.

FIG. 2 shows a section through a part of the guiding device according toFIG. 1, with an unsealed guide vane, and

FIG. 3 shows a section through the arrangement according to FIG. 2, witha guide vane which is sealed according to the disclosure.

DETAILED DESCRIPTION

The sealing of variable guide vanes, according to the disclosure, can beused on all turbomachines with guiding devices, for example exhaust gasturbochargers, power turbines, gas turbines or compressors, withvariable guide vanes.

FIG. 1 shows the turbine side of an exhaust gas turbocharger with aturbine wheel 10 which is arranged in a turbine housing. The turbinewheel comprises a hub 11 and rotor blades 12 which are fastened upon itor manufactured integrally with the hub. The turbine housing comprises agas inlet housing 21, a bearing housing 22, and also a partition 23 inthe back of the hub of the turbine wheel. The partition serves for thethermal shielding of the bearing housing from the hot turbine wheel. Itcan alternatively also be formed by parts of the bearing housing or thegas inlet housing.

A guiding device is arranged in the flow passage which leads to therotor blades. The guiding device comprises variable guide vanes 31 forcontrolling the exhaust gas flow 70. The guide vanes are rotatablymounted by a guide vane stem 32 in the turbine housing. The guide vanes31 can be rotated via an adjusting lever 41 around the axis of the guide35 vane stem 32. The adjusting lever is driven via an adjusting ring 42in order to position the guide vanes 31 in a defined set angle.

The guide vane stem 32 is mounted in the turbine housing with a smallclearance. The turbine housing, in the region of the bearing of theguide vane stem, advantageously comprises guide bushes 50 which have ahigh abrasion resistance and a good slidability. The guide bushes arepressed into the turbine housing and fixed.

As is apparent from FIG. 2 and FIG. 3, the guide vane stem has a bearing33 which is mounted inside the guide bush 50 in a sliding manner. Inaddition, the guide vane stem can have a further bearing, e.g, on theend opposite the guide vane. The axial support of the guide vanes as arule is carried out via one or two axial stops or via the end of theguide vane stem on the one side and via the guide vane profile on theother side. The axial locking of the guide vane can be ensured by meansof compression springs.

The guide vanes, which during operation are very intensely heated, mustbe installed with adequate radial clearance in the bearing bushes sothat in the hot operating state they do not seize in the bearing bushes.Both in the region of the bearings 33 and also radially outside themating contour 34 of the guide vanes, small gaps, through which leakageflows can flow out, ensue as a result.

In order to be able to avoid as far as possible leakage-related lossesof turbine efficiency, and to prevent penetration of hot exhaust gasesinto the bearings of the turbocharger, which are to be kept as cool aspossible, sealing air can be introduced into the cavities 61 in the backof the partition. This compressed air, which is significantly colder incomparison to the exhaust gases, can be externally supplied, or, asshown in FIG. 1, branched off at the compressor outlet and guided via asealing air passage 62 to the turbine side. The sealing air is guidedinto the cavities 61 and distributed along the entire circumference ofthe turbine. The sealing air can have an at least slightly higherpressure than the exhaust gas flow 70.

In the case of conventional guiding devices according to FIG. 2, hotgas, or, if present, sealing air, can escape from the cavities 61 intothe environment due to the radial clearance between the guide bush 50and the bearing 33 of the guide vane stem. A leakage flow 63 results.

This leakage flow is prevented according to the disclsoure by a sealingsleeve 80 being slipped onto the guide bush 50 according to FIG. 3. Thesealing sleeve according to the disclosure is advantageouslymanufactured, and can be cast, turned or milled, from a heat-resistantsteel. Depending upon the axial length of the axial gap which is to bebridged by the sealing sleeve, the sealing sleeve can be formed axiallylonger and more tubular, or else shorter and more annular. The sealingsleeve has a cylindrical collar, a radially projecting, at leastpartially encompassing collar with an axial stop. The sealing sleeve 80,in the exemplary embodiment which is shown, is supported by thecylindrical outside diameter of the guide bush 50. A possible radial gapbetween the sealing sleeve 80 and the guide bush 50 is tolerated to aminimum clearance. This radial clearance between parts which, duringoperation, do not move or hardly move in relation to each other, can bekept significantly smaller than the clearance between the bearing 33 ofthe guide vane stem and the guide bush. Therefore, only a small residualmass flow, if any at all, escapes through the fit. The additional axialcompression spring 90 ensures that the sealing sleeve is continuouslypressed onto the guide vane mating contour 34 and that the axial gap andalso the leakage flow are prevented as a result. The compression spring90 is clamped between an axial stop on the turbine housing 22 and theaxial stop of the cylindrical collar of the sealing sleeve 80. Thecompression spring 90 can additionally also undertake the axial securingof the guide vane by the guide vane profile being pressed by thecompression spring against the opposite wall of the flow passage oragainst another axial stop on the turbine housing.

In a further exemplary embodiment, which is not shown, the sealingsleeve can also be directly slipped onto a part of the turbine housing,for example if the guide bush of the guide vane bearing is not arrangedin an accessible manner, or is completely absent. In this case, thesealing sleeve would be supported by a cylindrical outside diameter of ahousing component. The sealing sleeve can alternatively also be radiallyguided inside the guide bush or inside a cylindrical recess of theturbine housing.

The sealing sleeve according to the disclosure, therefore, preventsdischarging of air or gases through the bearing of the guide vanes inexhaust gas turbines with or without sealing air supply, or in any otherturbomachine with rotatably mounted, variable guide vanes.

It will be appreciated by those skilled in the art that the presentinvention can be embodied in other specific forms without departing fromthe spirit or essential characteristics thereof. The presently disclosedembodiments are therefore considered in all respects to be illustrativeand not restricted. The scope of the invention is indicated by theappended claims rather than the foregoing description and all changesthat come within the meaning and range and equivalence thereof areintended to be embraced therein.

LIST OF DESIGNATIONS

10 Turbine wheel

11 Hub

12 Rotor blades

13 Shaft

21 Gas inlet housing

22 Bearing housing

23 Partition

31 Guide vane

32 Guide vane stem

33 Bearing

34 Mating contour

41 Adjusting lever

42 Adjusting ring, adjusting element

50 Guide bush

60 Sealing air flow

61 Cavity

62 Sealing air passage

63 Leakage

70 Hot gas flow

80 Sealing sleeve

90 Compression spring

1. A guiding device, comprising at least one guide vane with a guidevane stem which is rotatably mounted in a housing, and a sealing sleevebeing arranged between the housing and the guide vane stem for bridgingan axial gap.
 2. The guiding device as claimed in claim 1, wherein thesealing sleeve has a radially projecting collar with an axial stop. 3.The guiding device as claimed in claim 1, wherein the sealing sleeve ispressed against a mating contour of the guide vane by means of acompression spring.
 4. The guiding device as claimed in claim 3, whereinthe sealing sleeve has a radially projecting collar with an axial stop.5. The guiding device as claimed in claim 1, wherein the housingcomprises a guide bush for supporting the guide vane stem, and thesealing sleeve bridges a gap between the guide bush and the guide vanestem.
 6. A turbomachine with a guiding device, which comprises a guidevane with a guide vane stem which is rotatably mounted in a housing, anda sealing sleeve which is arranged between the housing and the guidevane stem for bridging an axial gap.
 7. The turbomachine as claimed inclaim 6, wherein the sealing sleeve has a radially projecting collarwith an axial stop.
 8. The turbomachine as claimed in claim 6, whereinthe sealing sleeve is pressed against a mating contour of the guide vaneby means of a compression spring.
 9. The turbomachine as claimed inclaim 8, wherein the sealing sleeve has a radially projecting collarwith an axial stop.
 10. The turbomachine as claimed in claim 6, whereinthe housing comprises a guide bush for supporting the guide vane stem,and the sealing sleeve bridges a gap between the guide bush and theguide vane stem.
 11. An exhaust gas turbocharger with a guiding device,which comprises at least one guide vane with a guide vane stem which isrotatably mounted in a housing, and a sealing sleeve which is arrangedbetween the housing and the guide vane stem for bridging an axial gap.12. The exhaust gas turbocharger as claimed in claim 11, wherein thesealing sleeve has a radially projecting collar with an axial stop. 13.The exhaust gas turbocharger as claimed in claim 11, wherein the sealingsleeve is pressed against a mating contour of the guide vane by means ofa compression spring.
 14. The exhaust gas turbocharger as claimed inclaim 13, wherein the sealing sleeve has a radially projecting collarwith an axial stop.
 15. The exhaust gas turbocharger as claimed in claim11, wherein the housing comprises a guide bush for supporting the guidevane stem, and the sealing sleeve bridges a gap between the guide bushand the guide vane stem.
 16. The guiding device as claimed in claim 4,wherein the housing comprises a guide bush for supporting the guide vanestem, and the sealing sleeve bridges a gap between the guide bush andthe guide vane stem.
 17. The turbomachine as claimed in claim 9, whereinthe housing comprises a guide bush for supporting the guide vane stem,and the sealing sleeve bridges a gap between the guide bush and theguide vane stem.
 18. The exhaust gas turbocharger as claimed in claim14, wherein the housing comprises a guide bush for supporting the guidevane stem, and the sealing sleeve bridges a gap between the guide bushand the guide vane stem.